In general You can setup up MOSFETs in parallell. My previous company used up to 400 Amps. The inverter used some 35 MOSFETs in parallell. Of course they need be of the same kind. If they come from the same production batch it will be the best and the FETs will share the current well.
Is there will be any need of aditional flyback diode to the motor?
Original schematic of bts7960b
The main differece would be that both bts7960b output pins will be conected to motor + and motor - to battery ground